PRIM CAST SHADOWS
According to User:Kelly_Linden in the JIRA SVC-1307 on 2008-02-25:
"Once, a long long time ago - beta, and maybe up to v 1.1 or 1.2 - all prims cast shadow on the ground only. Some time around 1.0 - 1.2 there was a minor graphics update that got rid of these shadows (among other things). However there was a flag that could be set on prims to *turn shadows off*, and this was not removed and I don't know why.
I'm not sure if llSetPrimitiveParams came around after or this was deprecated or just before, I think after. The prim shadows flag was included for "completeness", I assume, on the possibility it would do something. Or if I have my events backwards it really did do something for a very short time.
The flag has had no effect for years now. I will re-enable it as a no-op. It will always return 0 and setting it will have no effect.
So, I may be wrong in my history but this is how I think it happened. In any case, this parameter is gone and not coming back. I'll see about also changing the tool tip on the variable to indicate this."